Ex vivo
- Change in vessel diameter in response to vasoactive drugs.
- Activated signalling proteins which are associated with vasoresponsiveness.
- Receptors (quantity and function) which are associated with vasoresponsiveness.

- Timepoints

The phenylephrine challenge will be performed:
1. Before induction, before start medication (dobutamine, milrinone, noradrenalin)
2. Before induction, after start medication
3. After induction
4. After CPB, before emergence
5. On day 1 postoperative

The vasodilation test will be performed at the beginning of the surgery after placement of the arterial catheter and 1 day post-operatively.